This series and parallel sensor circuit was found in Popular Electronics from the 1990s. Any SCR can be used and the supply voltage depends on the load.
In this circuit of a 1968 publication the unijunction may be 2N2646 and the transistor BC548. The...
The purpose of this circuit is to improve a trigger circuit using a zener diode. The circuit was...
This interesting circuit of the American publication Electronics Handbook Volume XIII 1993 shows a...